1. Technical Field
The present invention relates to a multi-turn angle sensor which includes two or more resolvers having a structure which facilitates assembly.
2. Related Art
Japanese Patent Publication JP 3414953 A discloses a conventional multi-turn angle sensor which has a rotation shaft and a resolver which can sense a rotation angle of a shaft in one turn. This multi-turn angle sensor can sense a rotation angle of shaft for multiple turns, such as several hundred turns, by positioning the resolver on a speed reduction shaft whose speed is reduced from the speed of the rotation shaft.
FIG. 5 of the present application relates to FIG. 1 of JP 3414953 A, which is a cross-sectional view in an axial direction showing one embodiment of an absolute encoder in which three reluctance-type resolvers are coaxially placed. FIG. 6 is a cross-sectional view taken along the line I-I of FIG. 5.
The three resolvers, each of which is respectively formed by stators 61A, 63A, 65A and rotors 60, 62, 64, are arranged coaxially. An input shaft 19 is supported by casings 81, 84 via bearings 90, 95. A rotor 60 and non-magnetic gear 25 are connected to the input shaft 19 by interference fit. A shaft 20 is supported by the casings 81, 84 via bearings (not shown). Non-magnetic gears 26, 27, 29 are connected to the shaft 20 by interference fitting. A rotor 62 and non-magnetic gear 28 are connected to the input shaft 19 by interference fit via a bearing 93. A rotor 64 and non-magnetic gear 30 are connected to the input shaft 19 interference fitting via a bearing 94.
A speed reduction gear mechanism is formed by engagements between gear 25 with gear 26, gear 27 with gear 28, and gear 29 with gear 30. Gear 28 paired with rotor 62 and gear 30 paired with rotor 64 respectively. The speed reduction gear mechanism causes the rotor 62 to be rotated for every 24 rotations of the input shaft 19, and the rotor 64 to be rotated once for every 25 rotations of the input shaft 19.
As shown in FIG. 6, both of stator 63A and rotor 62 are formed by laminating thin plates of magnetic material produced by die blanking. The rotor 62 has a cylindrical shape arranged to eccentrically rotate about the center of a rotation shaft 80. The stator 63A is provided with four pole teeth 101 to 104, around each of which is wound one of four windings 111 to 114. Similarly, stator 61A (refer to FIG. 8) is provided with wirings 121 to 124 (not shown in FIG. 6), and stator 65A (refer to FIG. 8) with wirings 131 to 134 (not shown in FIG. 6). Each of these windings comprises excitation wiring and sensing wiring.
FIG. 7 shows a layout of wirings 111 to 114, 121 to 124, and 131 to 134. Circles 1-10 in FIG. 7 represent each of the connections to a connector 68 provided on printed circuit boards 51, 52, arranged between 61A and 63A and between 63A and 65A, respectively. The number with which each circle is labeled represents a pin number of a pin of the connector 68. FIG. 8 shows the relationships between the wiring shown in FIG. 6, and the excitation wiring numbers and sensing wiring numbers in FIG. 7. For example, FIG. 7 shows that the wiring 111 of the stator 63A is formed by an excitation wiring f1 and a sensing wiring a3. The connections between the wirings and between the wirings and the connector 68 are achieved by soldering connections onto the printed circuit boards 51, 52.
In the resolver formed by the stator 63A and rotor 62, a voltage in accordance with a rotation angle of the rotor is generated between pins 5 and 4 and between pins 6 and 4 of the connector 68 by applying a pulse voltage between pins 2 and 4 of the connector 68. An absolute position of the input shaft 19 for up to 25 turns can be sensed by interpolating a generated voltage. Further, the other two resolvers have structures similar to the resolver formed by the stator 63A and rotor 62, that is, the structure respectively formed by stator 61A and rotor 60, and stator 65A and rotor 64. These two resolvers can respectively sense an absolute position of the input shaft at one turn and 24 turns. A position of the input shaft 19 up to 600 turns can be accurately detected by numerically processing the values of the three absolute positions sensed by these three resolvers.